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M.P.H., Faculty of Health Sciences, University of the Witwatersrand, 2011 / Background: In Gauteng Province, South Africa, Sizwe Tropical Hospital (STH) is the designated centre for the specialized management of MDR-TB. But during the period covered by this study (2001-2002), all cases of TB (MDR-TB and NMDR-TB) were treated at STH. This was not according to the prescript of the National guidelines. This study describes the socio-demographic, treatment profile and treatment outcomes of MDR-TB patients seen and treated at STH during 2001 and 2002. Method: This was a cross sectional study involving retrospective review of records at STH. 281 systematically-sampled MDR-TB patient records were included in this study. Descriptive statistics were used to summarize the socio-demographic and treatment history characteristics and these were further analyzed to evaluate their relationship with MDR-TB treatment outcomes using Chi squared test of association. Means were compared using simple t-test. Results: The patients were majority black, unemployed, and living in townships and informal settlements. Sputum tests alone or combined with x-ray were most commonly used to diagnose MDR-TB (98%) at referring facilities; and the majority of patients arrived at STH with a referral note (98%). The median duration of stay at STH was 56 weeks (IQR 21-89). The majority of patients had a successful treatment outcome (75%); and amongst those with unsuccessful outcomes, a significant number had died (17%). Factors associated with poor iv outcomes in terms of death, default, treatment failure and transfer out were age groups (1-9 and 30-39), race, employment status, place of residence, housing structure, referral systems (referral note and feedback procedures) and HIV status. Discussion: The patients in this study had socio-demographic characteristics that facilitate TB transmission. There is a commendable referral system but various methods used to confirm MDR-TB and unjustified long duration of treatment prior to referral. Although in general the majority of patients have successful treatment outcomes, the policy guidelines of the management of MDR-TB are not implemented fully, and several factors associated to poor outcome are related to the health service and referral system. Recommendation: Effective adherence to the policy guidelines by health care providers and patients is recommended to improve treatment outcomes.

Background In 2006, South Africa documented its first outbreak of extensively drug-resistant (XDR-TB) in Tugela Ferry, Kwa-Zulu Natal. Delayed diagnosis of XDR-TB increases mortality, emphasizing the need or rapid diagnostics. The MTBDRsl assay rapidly identifies resistance to fluoroquinolones (FLQ) and aminoglycosides/capreomycin (AG/CP). Hospitalization provides the ideal opportunity for nosocomial infections of TB, including M/XDR-TB, with its associated morbidity and mortality. Occupational exposures amongst healthcare workers are also of concern. Rapid knowledge of second-line resistance patterns of these in-patients would allow for quick stratification and administration of individualized anti-chemotherapy treatment by clinicians, thereby reducing morbidity and mortality within this population. Methods ` A prospective cohort study was performed from admission sputum specimens collected from patients admitted to Sizwe Tropical Disease Hospital (Sizwe Hospital), the only M/XDR-TB referral hospital in Gauteng, South Africa. MTBDRplus (version 1) and MTBDRsl line probe assays (LPAs) were performed on all sputa, irrespective of smear positivity and subsequently on Mycobacteria Growth Indicator Tube (MGIT) isolates. The results from the LPAs were compared to the gold standard MGIT 960 culture and direct susceptibility testing (DST) results. Results From April 2011 to January 2012, 150 participants were recruited. Seventy-five (50.0%) were female, 91 (60.7%) were HIV-positive and 9 (6.00%) had an unknown HIV status. Of the MGIT cultures performed 71 (47.3%) were positive for Mycobacterium tuberculosis (MTB), 31 (20.7%) negative, 40 (26.7%) were contaminated and 8 (5.63%) were inadvertently discarded by the routinen laboratory. The proportion of smear-negative specimens in HIV- positive patients was not statistically significantly different to the smear-negatives in HIV-negative patients (57.1% vs. 46.0%; p=0.139). On phenotypic drug susceptibility testing, 47 (66.2%) were resistant to only isoniazid and rifampicin (MDR-TB), 10 (14.0%) were MDR-TB with added resistance to ofloxacin (pre-XDR-TB FLQ), 4 (5.63%) were MDR-TB with added resistance to kanamycin (pre-XDR-TB AG/CP), 4 (5.63%) were MDR-TB with added resistance to both ofloxacin and kanamycin (XDR-TB), 3 (4.23%) were mono-isoniazid resistant, 2 (2.82%) mono-rifampicin resistant, and 1 (1.41%) was TB-drug sensitive. No TB drug-sensitive sputum specimens were collected and used as a control group for the MTBDRplus (version 1) assay, thus only sensitivity indices and positive predictive values (PPVs) could be interpreted.All specimens collected were used as an inherent control group for the performance of the MTBDRsl assay, thus sensitivity and specificity indices together with the PPVs and NPVs, were calculated. From all sputum samples collected, including both smear-positives and smear-negative specimens, the sensitivity of the MTBDRplus (version 1) for RIF and INH was 98.1% for both drugs. Overall sensitivity for the MTBDRsl assay to detect ofloxacin (OFX) and kanamycin (KAN) resistance was 90.9% and 42.9%, respectively. The specificity was 100.0% and 95.7%, respectively. From smear-positive specimens, the sensitivity for OFX and KAN was 100.0% and 50.0%, respectively. The specificity was 100.0% and 96.8%, respectively. From smear-negative specimens the sensitivity was 50.0% and 33.3%, respectively. The specificity was 100.0% and 92.9%, respectively. From MGIT culture isolates, sensitivity for RIF and INH was 98.2% and 94.5% respectively. The sensitivity for OFX and KAN were 100.0% and 42.9%, respectively, whereas the specificity was 95.6% and 100.0%, respectively. Conclusion The performances of both LPAs correlate with other local and international publications. On direct, smear-positive sputa both LPAs perform well. From these, the MTBDRsl assay is a good rule-out test for detection of resistance to FLQ and AG/CP. For FLQ, it’s a good rule-in test: this indicates that the MTBDRsl assay can be used as a rapid screen for the onset of XDR-TB. As predicted, MTBDRsl does not perform well on smear-negative specimens, whereas the MTBDRplus (version 1) does. On cultures, both LPAs perform well.

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Solid oxide fuel cells operate at elevated temperature, oxidising fuel gases to generate electricity. The fuel gas streams in the fuel cell systems are rich in carbon and have very low oxygen potential. Under these conditions, alloys can undergo metal dusting, which causes pitting or general thinning of the alloys. This process is not yet fully understood. It is, hence, not possible to accurately predict the susceptibility of a particular alloy in the atmospheres relevant to SOFC. Model Fe-Cr and Fe-Ni-Cr alloys were exposed to test the hypothesis that cementite formation and its decomposition is necessary for metal dusting to occur. A series of ferritic and austenitic engineering alloys were also exposed to compare their dusting rates. Two specimens of each alloy were studied, one was etched in a H3PO4-15%H2SO4-21%H2O solution and the other was ground to a 600-grit finish. The alloys were exposed to a CO-26%H2-6%H2O gas mixture at 680oC under thermal cyclic conditions. The hot gas composition corresponded to ac = 2.9 and an oxygen potential high enough to oxidise chromium, but not iron or nickel. All the alloys were shown to undergo internal carburisation, metal dusting and coking once the protective chromium oxide scale was damaged. Fe-25Cr was less resistant than Fe-60Cr because of its lower chromium content. However, ferritic Fe-25Cr-based steels are more resistant to dusting than austenitic Fe-25Cr-25Ni. The present findings are consistent with the earlier conclusions that cementite formation is essential for dusting on ferritic steels and that dusting of austenitic alloys does not involve the prior formation of cementite and its decomposition. The onset of metal dusting was more accelerated for most austenitic engineering alloys (Alloy 800, Inconel 601, 690, 693 and Alloy 602CA) than for engineering ferritic steels (Fe-27Cr-0.001Y). However, the alloy with the best performance was austenitic Inconel 625, which was still protected by its Cr2O3 scale after 500 one-hour cycles. In both ferritic and austenitic chromia-formers alloys, the surface ground specimens were more resistant to metal dusting than the electropolished specimens. In contrast, ferritic alumina-formers with electropolished surfaces did not dust during the entire experimental periods of 1200 one-hour cycle, but the alloys with ground surfaces slowly underwent dusting attack. The coke deposits formed consisted largely of graphite nanotubes, containing small particles at the tube tips. These particles were identified as single crystal cementite, in the case of ferritic steels, and austenite, for the austenitic alloys. This is not in agreement with the currently accepted dusting model for ferritic steels that cementite decomposition yields iron particles, which catalyse coke deposition. EDX analysis of the cementite particles, showed that the only metal detected was iron, thus differing in chemistry from the (Fe,Cr)3C surface layer. Similarly, the austenite particles contained only nickel and iron, differing in chemistry from the disintegrated alloy surfaces. These results suggested that the particles were formed in the coke in the carbon-supersaturated gas, rather than disintegration of the alloy surface layer. Strong orientation relationships were determined between the graphite and cementite particles; however, no clear crystallographic relationship was deduced between the graphite and austenite. Relative alloy performance appears consistent using the present multiple one-hour cycle and the results of others using a smaller number of lengthy cycles. Hourly thermal cycling was shown to accelerate the dusting onset for both electropolished chromia-formers and surface ground alumina-formers. Protective oxide scales spall at a critical thickness and carbon attack results when the alloy surfaces are depleted of scale-forming elements and healing becomes impossible. On this basis, analytical models were developed and used to predict the incubation periods for oxide failure and the subsequent carbon attack. Upon testing, these models were, however, found to be not qualitatively meaningful in predicting the onset of dusting observed in the present study. Gross oversimplifications involved in the model and the absence of reliable data for many parameters required for the computations prevented even an approximate quantitative prediction.